During the past year, our research has included studies of: (1) Etiological mechanisms underlying individual differences in alcohol consumption including the effects of age, alcohol exposure, setting, sex, and paternal genetic contributions; (2) The effect of early experience on the development of the nervous system and on the acquisition of social competence and aggressive behaviors; (3) The relationship between serotonin (SHT) and aggression in laboratory and free-ranging rhesus macaques. To obtain a subject pool of aggressive rhesus macaques, we continued to investigate free-ranging adolescent males drawn from a subject pool of 4500 free-ranging rhesus macaques; (4) Developmental patterns of rhesus macaques selectively bred for extremes in CSF 5-HIAA. A major part of the past year has involved the continued investigation of the infants (now in their late childhood) that were selectively bred for extremes in CSF 5-HIAA concentration. Both parents and the infants have been carefully assessed to investigate parental genetic contributions to excessive aggression and alcohol consumption; (5) Continued use of the PET scan paradigm developed over the past two years to assess neurobiological differences in aggression in intact subjects.